The US protects its interests, not nations per se

"Of course, the rest of the world rarely comes to the rescue of anybody anyway and it usually falls on the U.S. to protect other nations simply because we are stronger and can."

I disagree with this point.

Vietnam rescued Cambodia from Pol Pot, but never got credit or international recognition for that, because it was country with a communist government that beat the U.S. Their operation to save their neighbour Cambodia cost them several 100 thousand dead troops (not counting civilian casualties), as China went in to protect Pol Pot who was their ally. The US actually helped install Pol Pot, and wasn't about to step in in an arena where they'd already lost a war. Of course one could also argue that they didn't step in because they didn't have the support of the people with all that anti-war sentiment going on. The US enforced an international boycott of Vietnam that lasted 25 years.

In 1989, China massacred 1000s of students in Tienamen Square demonstrating for freedom, idolizing US models of democracy. They even erected a replica of the statue of liberty. The actions the US government took against China amounted to not even a slap on the wrist. The US needed to continue doing trade with China.

The US had enough popular support to step in in Rwanda in 1994, when 1 million people were killed in a 4 month period, but did nothing.

I don't have time now, but there are many such examples, where the US can step in, has popular support to do so, but does nothing. It does however, send troops to strategic locations like Panama and Somalia.